Field
Integrated circuit packaging.
Description of Related Art
Accurately measuring molding material thickness associated with integrated circuit die packaging is a valuable tool for process control and monitoring during assembly technology development and manufacturing. Out-of-specification molding thickness can potentially lead to downstream low yield and reliability issues. As an example, yield loss is observed during surface mount technology (SMT) processes due to high warpage variation of a die relative to a package such as with a system on chip (SOC) package. Key contributors for high warpage variation in an SOC package is the molding thickness variation. Developing non-destructive measurement solutions for molding thickness is inherently challenging due to its low-transparency nature in visible and infrared (IR) wavelength and the relatively large thickness of the molding material. Existing inline inspection metrologies based on optical or X-ray do not have the capability to inspect the molding material due to high beam absorption or low contrast. Acoustic microscopy requires parts to be immersed in water thus not suited for inline monitoring. One method available to measure molding thickness is physical failure analysis (FA) cross-section which is destructive and low-throughput and thus not amenable to inline process monitoring.